When reducing initial empty rules, Bison parser read an initial

location that is not defined.  This results in garbage, and that
affects Bison's own parser.  Therefore we need (i) to extend Bison
to support a means to initialize this location, and (ii) to use
this CVS Bison to fix CVS Bison's parser.
* src/reader.h, reader.c (epilogue_augment): Remove, replace
with...
* src/muscle_tab.h, src/muscle_tab.c (muscle_code_grow): this.
* src/parse-gram.y: Adjust.
(%initial-action): New.
(%error-verbose): Since we require CVS Bison, there is no reason
not to use it.
* src/scan-gram.l: Adjust.
* src/Makefile.am (YACC): New, to make sure we use our own parser.
* data/yacc.c (yyparse): Use b4_initial_action.

src/parse-gram.h

@@ -1,4 +1,4 @@
-/* A Bison parser, made by GNU Bison 1.875b.  */
+/* A Bison parser, made by GNU Bison 1.875c.  */
 
 /* Skeleton parser for Yacc-like parsing with Bison,
    Copyright (C) 1984, 1989, 1990, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
@@ -51,29 +51,30 @@
      PERCENT_EXPECT = 276,
      PERCENT_FILE_PREFIX = 277,
      PERCENT_GLR_PARSER = 278,
-     PERCENT_LEX_PARAM = 279,
-     PERCENT_LOCATIONS = 280,
-     PERCENT_NAME_PREFIX = 281,
-     PERCENT_NO_LINES = 282,
-     PERCENT_NONDETERMINISTIC_PARSER = 283,
-     PERCENT_OUTPUT = 284,
-     PERCENT_PARSE_PARAM = 285,
-     PERCENT_PURE_PARSER = 286,
-     PERCENT_SKELETON = 287,
-     PERCENT_START = 288,
-     PERCENT_TOKEN_TABLE = 289,
-     PERCENT_VERBOSE = 290,
-     PERCENT_YACC = 291,
-     TYPE = 292,
-     EQUAL = 293,
-     SEMICOLON = 294,
-     PIPE = 295,
-     ID = 296,
-     ID_COLON = 297,
-     PERCENT_PERCENT = 298,
-     PROLOGUE = 299,
-     EPILOGUE = 300,
-     BRACED_CODE = 301
+     PERCENT_INITIAL_ACTION = 279,
+     PERCENT_LEX_PARAM = 280,
+     PERCENT_LOCATIONS = 281,
+     PERCENT_NAME_PREFIX = 282,
+     PERCENT_NO_LINES = 283,
+     PERCENT_NONDETERMINISTIC_PARSER = 284,
+     PERCENT_OUTPUT = 285,
+     PERCENT_PARSE_PARAM = 286,
+     PERCENT_PURE_PARSER = 287,
+     PERCENT_SKELETON = 288,
+     PERCENT_START = 289,
+     PERCENT_TOKEN_TABLE = 290,
+     PERCENT_VERBOSE = 291,
+     PERCENT_YACC = 292,
+     TYPE = 293,
+     EQUAL = 294,
+     SEMICOLON = 295,
+     PIPE = 296,
+     ID = 297,
+     ID_COLON = 298,
+     PERCENT_PERCENT = 299,
+     PROLOGUE = 300,
+     EPILOGUE = 301,
+     BRACED_CODE = 302
    };
 #endif
 #define GRAM_EOF 0
@@ -98,35 +99,36 @@
 #define PERCENT_EXPECT 276
 #define PERCENT_FILE_PREFIX 277
 #define PERCENT_GLR_PARSER 278
-#define PERCENT_LEX_PARAM 279
-#define PERCENT_LOCATIONS 280
-#define PERCENT_NAME_PREFIX 281
-#define PERCENT_NO_LINES 282
-#define PERCENT_NONDETERMINISTIC_PARSER 283
-#define PERCENT_OUTPUT 284
-#define PERCENT_PARSE_PARAM 285
-#define PERCENT_PURE_PARSER 286
-#define PERCENT_SKELETON 287
-#define PERCENT_START 288
-#define PERCENT_TOKEN_TABLE 289
-#define PERCENT_VERBOSE 290
-#define PERCENT_YACC 291
-#define TYPE 292
-#define EQUAL 293
-#define SEMICOLON 294
-#define PIPE 295
-#define ID 296
-#define ID_COLON 297
-#define PERCENT_PERCENT 298
-#define PROLOGUE 299
-#define EPILOGUE 300
-#define BRACED_CODE 301
+#define PERCENT_INITIAL_ACTION 279
+#define PERCENT_LEX_PARAM 280
+#define PERCENT_LOCATIONS 281
+#define PERCENT_NAME_PREFIX 282
+#define PERCENT_NO_LINES 283
+#define PERCENT_NONDETERMINISTIC_PARSER 284
+#define PERCENT_OUTPUT 285
+#define PERCENT_PARSE_PARAM 286
+#define PERCENT_PURE_PARSER 287
+#define PERCENT_SKELETON 288
+#define PERCENT_START 289
+#define PERCENT_TOKEN_TABLE 290
+#define PERCENT_VERBOSE 291
+#define PERCENT_YACC 292
+#define TYPE 293
+#define EQUAL 294
+#define SEMICOLON 295
+#define PIPE 296
+#define ID 297
+#define ID_COLON 298
+#define PERCENT_PERCENT 299
+#define PROLOGUE 300
+#define EPILOGUE 301
+#define BRACED_CODE 302
 
 
 
 
 #if ! defined (YYSTYPE) && ! defined (YYSTYPE_IS_DECLARED)
-#line 75 "parse-gram.y"
+#line 80 "parse-gram.y"
 typedef union YYSTYPE {
   symbol *symbol;
   symbol_list *list;
@@ -135,8 +137,8 @@ typedef union YYSTYPE {
   assoc assoc;
   uniqstr uniqstr;
 } YYSTYPE;
-/* Line 1268 of yacc.c.  */
-#line 140 "y.tab.h"
+/* Line 1285 of yacc.c.  */
+#line 142 "y.tab.h"
 # define yystype YYSTYPE /* obsolescent; will be withdrawn */
 # define YYSTYPE_IS_DECLARED 1
 # define YYSTYPE_IS_TRIVIAL 1